The shores of Lake Baikal in Siberia, the world's largest body of fresh water and popular tourist destination, are covered with rotting algae dangerous to its unique ecosystem.

Baikal is getting
increasingly contaminated by spirogyra, which could pose a threat
to the purity of its waters.

Spirogyra is not native to Baikal's ecosystem. It thrives on
biological waste which, according to ecologists, is provided in
abundance by the sewage facilities of the local holiday centers,
as well as private boats.

Now, most of Baikal's shores are covered in rotting spirogyra.
Only the western shore remains clean.

"It has never been detected previously in such a mass
abundance. Spirogyra is completely occupying more than 50 percent
of the coastal area of Lake Baikal," says Oleg Timoshkin
from the Limnological Institute of the Russian Academy of
Sciences. The institute researches the flora and fauna of
Siberian lakes.

"Last year, there was more than 1,500 tonnes of rotting
algae. Unfortunately, I can definitely say that Baikal is ill.
Seriously ill."

[Video showing algae on the bottom of Lake Baikal. Caption at
01:32 says 'This is what the same part of the lake bottom looked
like several years ago".]

Baikal's unequaled purity is in part due to an endemic sponge,
lubomirskia baicalensis, which feeds by filtering water. The
spirogyra, while harmless by itself, infects the sponge, thus
threatening the lake's pristine state.

But the alien algae aren't the only threat Baikalis facing at the
moment. Its water level is at a record low – 5cm below the
critical level of 456 meters, according to a source in the local
emergency services who spoke to RIA Novosti. The level hit
critical just three weeks ago.

This has led to the Republic of Buryatia, whose territory
includes Baikal's eastern shore, declaring a state of ecologic
emergency. The officials have also asked the local population to
start saving water.

They say the draining could cause irreversible damage to the
lake's unique ecosystem and leave almost 30,000 locals without
water. Some local ecologists blame energy companies for
over-using Baikal's water reserves.

"At the beginning of the season, in April- May, hydroelectric
power plants flushed increased amounts of water, while they
should have been saving water in the lake," said Endon
Garmaev from the Siberian branch of the Russian Academy of
Sciences, as cited by Rosbalt news agency. "The flush
continued throughout the summer. Energy from hydroelectric plants
is the cheapest, and [nearby city] Irkutsk power companies are
after a bigger profit."

However, experts from Irkutsk Region, on Baikal's western shore,
say there's nothing to worry about, and the dropping water levels
are a natural result of ecological cycles, following an unusually
dry summer.

"Throughout the existence of the Irkutsk hydroelectric power
plant, despite several emergency cases, nothing happened to the
lake's biosystem", claims Mikhail Grachev, director of the
Limnological Institute, as cited by lenta.ru.

Baikal is the world's oldest freshwater lake, about 25 million
years old. It holds one-fifth of the entire planet's freshwater
reserves. The importance of its protection has been stressed by
UNESCO, which declared it a World Heritage site in 1996.